Change in water activity of some Turkish hazelnut cultivars at different moistures and temperatures

Abstract

Objective: Observation of the changes in water activity values of some Turkish hazelnut cultivars at different moisture levels (ML) at varying ambient temperatures. Thus, especially in hazelnut storage and transfer processes, regulations regarding the protection of the quality of the product under changing humidity and temperature conditions are foreseen. Materials and Methods: In this study, water activity (aw) of Tombul, Palaz, Çakıldak and Kalınkara hazelnuts were determined at different ML (2, 4, 6, 8, 9 and 12%) and different temperatures (20, 21, 22, 23, 24, 25, 26, 27, 28, 29 and 30°C). Regression equations were generated to estimate aw values of hazelnuts with a known moisture at different ambient temperatures. Results: Considering the entire temperatures, it was observed that a unit (1%) increase in moisture yielded 0.055 - 0.062 unit increases in Çakıldak cultivar, 0.052 - 0.055 unit increases in Palaz cultivar, 0.047 - 0.050 unit increases in Tombul cultivar and 0.047 - 0.048 unit increases in Kalınkara cultivar. Different aw values were observed at the same ML of the cultivars and generally the aw values were tended to increase with increasing temperatures. Conclusion: It was concluded that water activity influenced several quality parameters (color, lipid oxidation and etc.). Present findings revealed that hazelnut cultivars with the same moisture levels might have different water activity values. The fact that the varieties at the same ML have different water activity values indicates that it will be more objective to use the water activity value in storage or shelf life studies. In the calculations made using the obtained formula, it was seen that Palaz and Kalınkara (at the same ML) cultivars had higher aw values than the other two cultivars. For this reason, it is thought that storing Palaz and Kalınkara separately from Tombul and Çakıldak cultivars may reduce the possible risks.